基坑开挖塑性导致不收敛问题：采用的是剑桥模型，移除地连墙所占土体时，约束了被移除土体的水平位移和竖向位移。接着是激活地连墙，就在激活地连墙的时候呢，塑性变形过大，不收敛。换成弹性模型没有问题的。
我用剑桥模型不收敛的时候有以下提示：
1.The slave surfaces, assembly__pickedsurf273 and assembly_soil-wall-left intersect each other and are paired with master surfaces that intersect each other as well，，，，
2.OVERCONSTRAINT CHECKS: THERE ARE 19267 BOUNDARY CONDITIONS SPECIFIED IN THIS MODEL. OVERCONSTRAINT CHECKS FOR BOUNDARY CONDITIONS SPECIFIED ON SLAVE NODES OF RIGID BODIES, OF *TIE OPTIONS, OR OF *COUPLING OPTIONS REQUIRE 7 Mb OF MEMORY. IF THIS IS A PROBLEM, PLEASE TURN OFF OVERCONSTRAINT CHECKS USING *CONSTRAINT CONTROLS, NO CHECKS or INCREASE THE MEMORY USED BY THE PRE-PROCESSOR.
3.One or more *TIE dependent nodes have specified boundary conditions. The boundary conditions from these nodes will be transferred to the associated *TIE independent nodes.The *TIE dependent and independent nodes have been identified in node set WarnNodeOverconBoundTieMov.
4.For *tie pair (assembly_soil-wall-b-assembly_wall-bottom), adjustment was specified but no node was adjusted more than the adjustment distance = 2.22000e-16.
5.No pore fluid flow will occur across slave surface assembly__pickedsurf273 and master surface assembly__pickedsurf272.
6.Displacement increment for contact is too big.
7.There is zero VOL. FLUX everywhere in the model based on the default criterion. ，，，，
8.The plasticity/creep/connector friction algorithm did not converge at 1 points
